Physiological responses of wild type and putrescine-overproducing transgenic cells of poplar to variations in the form and concentration of nitrogen in the medium

Abstract

We determined: (a) the physiological consequences of overproduction of putrescine in transgenic poplar (Populus nigra x mnrimoviczir) cells expressing an omithine decarboxylase transgene; and (b) effects of variation in nitrogen (N) concentration of the medium on cellular polyamine concentration in transgenic and non-transgenic cells. Cells grown in the presence of supplemental (to the normal concentrations of N sources in the growth medium) and reduced amounts of NH₄N0₃ and KN0₃ were used to study effects on membrane permeability, mitochondria1 respiratory activity, protein accumulation, growth rates and changes in cellular polyamine concentration. The N concentration of the MS medium was not a limiting factor for continued overproduction of putrescine in transgenic cells. However, continued supplies of NH₄ and NO₃ were required to maintain homeostatic amounts of putrescine in both cell lines. The presence of high amounts of putrescine in transgenic cells had significant effects on the physiological parameters measured. Compared with nontransgenic cells, transgenic cells had greater plasma membrane permeability, less tolerance to NH₄NO₃, more tolerance to KNO₃, and accumulated higher amounts of soluble protein.

Citation

Minocha, Rakesh; Lee, Jae Soon; Long, Stephanie; Bhatnagar, Pratiksha; Minocha, Subhash C. 2004. Physiological responses of wild type and putrescine-overproducing transgenic cells of poplar to variations in the form and concentration of nitrogen in the medium. Tree Physiology. 24: 551-560.